This signal box controlled the south end of the Trabboch Colliery loop, on the east side of the line, and access to the Garrockhill Colliery loading point, a set of looped sidings running south parallel to the line on its west side with access at the north end. This colliery was to the south and connected to the loading point by a tramway system running on a viaduct. A further portion of the tramway extended further south to Duchray Colliery. The north end of the Trabboch loop was at Trabboch Signal Box. Garrockhill box closed in 1948.